Question:

A table fan rotating at a speed of 2400 rpm is switched off and the resulting variation of revolution/minute with time is shown in figure. The total number of revolutions of the fan before it, comes to rest is

Updated On: Apr 15, 2024
  • 160
  • 280
  • 380
  • 420
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The Correct Option is B

Solution and Explanation

Total number of revolutions $=$ area under $n-t$ graph $=\frac{1}{2} \times 8 \times \frac{1800}{60}+8 \times \frac{600}{60}+\frac{1}{2} \times 16 \times \frac{600}{60}$ $=120+80+80=280$
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Concepts Used:

System of Particles and Rotational Motion

  1. The system of particles refers to the extended body which is considered a rigid body most of the time for simple or easy understanding. A rigid body is a body with a perfectly definite and unchangeable shape.
  2. The distance between the pair of particles in such a body does not replace or alter. Rotational motion can be described as the motion of a rigid body originates in such a manner that all of its particles move in a circle about an axis with a common angular velocity.
  3. The few common examples of rotational motion are the motion of the blade of a windmill and periodic motion.